Multi-carrier transmitting apparatus and multi-carrier transmitting method

ABSTRACT

A coding section  101  turbo-codes transmit data and outputs parity bit data, and systematic bit data for which good quality is required. A modulation section  102  modulates the parity bit data and systematic bit data. A subcarrier allocation section  103  rearranges the transmit data so that systematic bit data is allocated to subcarriers in the vicinity of the center frequency and parity bit data is allocated to subcarriers in the vicinity of both ends. An OFDM section  104  performs orthogonal frequency division multiplexing of the transmit data, and allocates parity bit data and systematic bit data to respective subcarriers. By this means, it is possible to improve significantly the error rate characteristics of transmit data for which good quality is required, and prevent degradation of the quality of transmit data for which good quality is required.

TECHNICAL FIELD

The present invention relates to a multicarrier transmitting apparatusand multicarrier transmitting method.

BACKGROUND ART

Error correction coding methods include turbo coding, which has beenadopted as standard in 3GPP. A feature of this turbo coding is thatextremely good error rate characteristics can be obtained compared withother error correction methods.

OFDM is an effective communication method for the fourth generation, andis regarded as important as a fourth-generation communication method. Onthe other hand, since OFDM communication ceases to be possible at all inthe presence of interference, the OFDM-CDMA communication method isknown that combines CDMA and OFDM and enables communication to beperformed even when interference from another cell is present byreducing interference from other cells by means of despreadingprocessing.

Error rate characteristics can be improved by using a combination ofturbo coding and the OFDM communication method, or a combination ofturbo coding and the OFDM-CDMA communication method, in this way.

However, a problem with a conventional multicarrier transmittingapparatus and multicarrier transmitting method is that, although errorrate characteristics can be improved to some extent by combining turbocoding and the OFDM communication method, or turbo coding and theOFDM-CDMA communication method, when simultaneous transmission isperformed using a plurality of channels, mutual interference occursbetween transmit signals of different channels, and there is a limit tothe improvement in error rate characteristics.

DISCLOSURE OF INVENTION

It is an object of the present invention to provide a multicarriertransmitting apparatus and multicarrier transmitting method that make itpossible to improve significantly the error rate characteristics oftransmit data for which good quality is required, and preventdegradation of the quality of transmit data for which good quality isrequired.

This object can be achieved by allocating transmit data for which goodquality is required, such as systematic bits, to subcarriers in thevicinity of the center frequency.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram showing the configuration of a multicarriertransmitting apparatus according to Embodiment 1 of the presentinvention;

FIG. 2 is a block diagram showing the configuration of a coding sectionaccording to Embodiment 1 of the present invention;

FIG. 3 is a drawing showing data allocation for each subcarrier;

FIG. 4 is a block diagram showing the configuration of a multicarriertransmitting apparatus according to Embodiment 2 of the presentinvention;

FIG. 5 is a schematic diagram showing data allocation for eachsubcarrier;

FIG. 6 is a drawing showing data allocation for each subcarrier;

FIG. 7 is a block diagram showing the configuration of a multicarriertransmitting apparatus according to Embodiment 3 of the presentinvention;

FIG. 8 is a drawing showing the configuration of a control sectionaccording to Embodiment 3 of the present invention;

FIG. 9 is a block diagram showing the configuration of a multicarriertransmitting apparatus according to Embodiment 4 of the presentinvention;

FIG. 10 is a block diagram showing the configuration of a multicarriertransmitting apparatus according to Embodiment 5 of the presentinvention;

FIG. 11 is a block diagram showing the configuration of a multicarriertransmitting apparatus according to Embodiment 6 of the presentinvention;

FIG. 12 is a drawing showing data allocation for each subcarrier;

FIG. 13 is a block diagram showing the configuration of a multicarriertransmitting apparatus according to Embodiment 8 of the presentinvention;

FIG. 14 is a drawing showing a signal spectrum for one subcarrier;

FIG. 15 is a drawing showing a signal spectrum;

FIG. 16 is a schematic diagram showing data allocation for eachsubcarrier;

FIG. 17 is a block diagram showing the configuration of a multicarriertransmitting apparatus according to Embodiment 9 of the presentinvention;

FIG. 18 is a block diagram showing the configuration of a delaydistribution information generation section according to Embodiment 9 ofthe present invention;

FIG. 19 is a block diagram showing the configuration of a multicarriertransmitting apparatus according to Embodiment 10 of the presentinvention;

FIG. 20 is a block diagram showing the configuration of a multicarriertransmitting apparatus according to Embodiment 11 of the presentinvention; and

FIG. 21 is a schematic diagram showing data allocation for eachsubcarrier.

BEST MODE FOR CARRYING OUT THE INVENTION

With reference now to the accompanying drawings, embodiments of thepresent invention will be explained in detail below.

Embodiment 1

FIG. 1 is a drawing showing the configuration of a multicarriertransmitting apparatus 100 according to this embodiment, FIG. 2 is adrawing showing the configuration of a coding section 101, and FIG. 3 isa drawing showing transmit data allocation for each subcarrier.

Multicarrier transmitting apparatus 100 is mainly composed of codingsection 101, a modulation section 102, a subcarrier allocation section103, an OFDM section 104, an amplifier 105, an antenna 106, an FFTsection 107, a demodulation section 108, and a transmission powercontrol section 109.

Coding section 101, which is a dividing section, may be a turbo coder,for example, and outputs part of the input transmit data uncoded tomodulation section 102 as systematic bit data, performs recursiveconvolutional coding on the remaining part of the input transmit data,and outputs this to modulation section 102 as parity bit data. Codingsection 101 will be described in detail later herein.

Modulation section 102 executes respective modulation processing on thesystematic bit data, which is high-quality transmit data, and parity bitdata, which is ordinary transmit data, input from coding section 101,and outputs the modulated systematic bit data and parity bit data tosubcarrier allocation section 103. The modulation method used inmodulation section 102 is changed adaptively according to the channelquality, with either 16QAM or QPSK being used. Then both systematic bitdata and parity bit data are modulated by means of the same modulationmethod. The modulation method is not limited to 16QAM or QPSK, and amodulation method other than 16QAM or QPSK may be used.

Subcarrier allocation section 103, which is a rearranging section,performs rearrangement of systematic bit data and parity bit data sothat, within the subcarrier frequency range in which transmit data isallocated, systematic bit data input from modulation section 102 isallocated to subcarriers in the vicinity of the center frequency, andparity bit data is allocated to subcarriers in the vicinity of each end.The ranges on the subcarrier frequency axis to which systematic bit dataand parity bit data are allocated are changed in accordance with anadjacent channel interference wave reception level input to subcarrierallocation section 103. That is to say, when the adjacent channelinterference wave reception level is high, transmit data rearrangementis performed so that systematic bit data is allocated to subcarriersin-a narrow frequency range including center frequency F1, and when theadjacent channel interference wave reception level is low, transmit datarearrangement is performed so that systematic bit data is allocated tosubcarriers in a wide frequency range including center frequency F1.Then subcarrier allocation section 103 outputs transmit data composed ofthe rearranged systematic bit data and parity bit data to OFDM section104.

OFDM section 104, which is an orthogonal frequency division multiplexingsection, performs orthogonal frequency division multiplexing andgenerates an OFDM signal by executing serial-parallel conversionprocessing, followed by inverse fast Fourier transform (IFFT)processing, on the transmit data input from subcarrier allocationsection 103, and transmits the generated OFDM signal from antenna 106via amplifier 105. The method of allocating transmit data for eachsubcarrier will be described in detail later herein.

Amplifier 105 transmits transmit data input from OFDM section 104 fromantenna 106 at predetermined transmission power controlled bytransmission power control section 109. At this time, systematic bitdata allocated to subcarriers in the vicinity of the center frequency istransmitted at transmission power greater than the transmission power ofparity bit data allocated to subcarriers in the vicinity of both ends.

FFT section 107 executes fast Fourier transform (FFT) processing onreceive data received by antenna 106, and outputs the resulting data todemodulation section 108.

Demodulation section 108 obtains receive data by demodulating thereceive data input from FFT section 107, and outputs the demodulatedreceive data to transmission power control section 109.

Transmission power control section 109, which is a transmission powersetting section, determines transmission power from the receive datainput from demodulation section 108, and performs transmission powercontrol for amplifier 105 so that transmit data is transmitted at thedetermined transmission power. Transmission power control section 109performs transmission power control so that the transmission power ofsystematic bit data allocated to subcarriers in the vicinity of thecenter frequency is greater than the transmission power of parity bitdata allocated to subcarriers of the frequencies at both ends. By thismeans, transmission power can be varied according to channel quality.Therefore, transmit data is transmitted at transmission power that isbased on channel quality.

Next, the configuration of coding section 101 will be described indetail using FIG. 2. Coding section 101 is mainly composed of aninterleaver 201, a convolutional coding section 202, and a convolutionalcoding section 203.

Interleaver 201 performs interleaving, which is rearrangementprocessing, of transmit data, and outputs the resulting data toconvolutional coding section 203.

Convolutional coding section 202 performs recursive convolutional codingof part of the transmit data, and outputs the resulting data tomodulation section 102. The output from convolutional coding section 202is parity bit data.

Convolutional coding section 203 performs recursive convolutional codingof part of the transmit data input from interleaver 201, and outputs theresulting data to modulation section 102. The output from convolutionalcoding section 203 is parity bit data. Also, part of the transmit datainput to coding section 101 is output directly without being coded. Thisoutput is systematic bit data.

Transmit data allocation for each subcarrier will now be described usingFIG. 3. In FIG. 3, subcarriers are arranged on the frequency axis, andsubcarriers are allocated to the same frequency width to the left andright of center frequency F1. Reference code L1 in FIG. 3 indicates thesubcarrier frequency range to which transmit data composed of systematicbit data and parity bit data is allocated. Subcarriers 301 and 302 arethe end subcarriers. The subcarriers from subcarrier 304 to subcarrier305 are subcarriers in the vicinity of the center frequency. Thesubcarriers from subcarrier 301 to subcarrier 306 and from subcarrier302 to subcarrier 307 are subcarriers in the vicinity of the ends.

Adjacent channel interference waves are present at frequencies lowerthan subcarrier 301 (on the left in FIG. 3) and frequencies higher thansubcarrier 302 (on the right in FIG. 3). Therefore, the effect ofadjacent channel interference waves gradually increases from centerfrequency F1 toward subcarriers 301 and 302, and consequently error ratecharacteristics gradually degrade from center frequency F1 towardsubcarriers 301 and 302.

After transmit data has undergone frequency division multiplexingprocessing by OFDM section 104, parity bit data is allocated tosubcarriers in frequency ranges W1 and W3, and systematic bit data isallocated to subcarriers in frequency range W2. Subcarrier frequencyrange W2 to which systematic bit data is allocated is changed accordingto the adjacent channel interference wave reception level. That is tosay, when the adjacent channel interference wave reception level ishigh, frequency range W2 to which systematic bit data is allocated ismade narrower, and when the adjacent channel interference wave receptionlevel is low, frequency range W2 to which systematic bit data isallocated is made wider.

Another example will now be described in which transmit data is otherthan systematic bit data and parity bit data. As another example inwhich transmit data is other than systematic bit data and parity bitdata, this embodiment can also be applied to a case where transmit datafor which good quality is required, such as control information orretransmission information, and transmit data other than controlinformation or retransmission information, for which normal quality issufficient, are allocated to respective subcarriers. In this case,coding section 101 need not necessarily be a turbo coder, and a coderother than a turbo coder can be used. Control information is informationused for communication control, and retransmission information isinformation for having data transmitted again when data cannot bedemodulated correctly due to the occurrence of an error on the receivingside. Coding section 101 divides transmit data into transmit data forwhich good quality is required and transmit data for which normalquality is sufficient, and outputs these transmit data to subcarrierallocation section 103.

Subcarrier allocation section 103 rearranges the transmit data so thattransmit data for which good quality is required is allocated tosubcarriers in the vicinity of center frequency F1, and transmit datafor which normal quality is sufficient is allocated to subcarriers inthe vicinity of both ends.

After transmit data has undergone frequency division multiplexingprocessing by OFDM section 104, transmit data for which good quality isrequired is allocated to subcarriers in frequency range W2 in thevicinity of center frequency F1, and transmit data for which normalquality is sufficient is allocated to subcarriers in frequency ranges W1and W3 in the vicinity of both ends.

Thus, according to a multicarrier transmitting apparatus andmulticarrier transmitting method of this embodiment, systematic bit datais allocated to subcarriers in the vicinity of the center frequency, andparity bit data is allocated to subcarriers in the vicinity of bothends, making it possible to improve the error rate characteristics oftransmit data for which good quality is required, and to improve thecommunication quality of transmit data for which good quality isrequired. Also, transmit data for which good quality is required, suchas control information or retransmission information, is allocated tosubcarriers in the vicinity of the center frequency, and transmit dataother than control information or retransmission information, for whichnormal quality is sufficient, is allocated to subcarriers in thevicinity of both ends, making it possible to improve the error ratecharacteristics of transmit data for which good quality is required, andto improve the communication quality of transmit data for which goodquality is required, such as control information or retransmissioninformation. Furthermore, transmission power control is performed sothat the transmission power of systematic bit data allocated tosubcarriers in the vicinity of the center frequency is greater than thetransmission power of parity bit data allocated to subcarriers offrequencies at both ends, enabling the error rate characteristics ofsystematic bit data to be improved.

In this embodiment, it has been assumed that transmission power controlrelated to channel quality is performed using demodulation results, butthis is not a limitation, and transmission power may also be setvariably independently of demodulation results. In this embodiment,also, it has been assumed that both the transmission power of systematicbit data and the transmission power of parity bit data are madevariable, but this is not a limitation, and the transmission power ofonly systematic bit data or only parity bit data may be made variable.Furthermore, in this embodiment the transmission power of systematic bitdata is made greater than the transmission power of parity bit data, butthis is not a limitation, and the transmission power of systematic bitdata and the transmission power of parity bit data may be made the same,or the transmission power of parity bit data may be made greater thanthe transmission power of systematic bit data. Moreover, transmit datais not limited to systematic bit data and parity bit data, and may bedata other than systematic bit data and parity bit data for which therequired quality differs. In this case, a coder other than a turbo codercan be used for coding section 101.

Embodiment 2

FIG. 4 is a drawing showing the configuration of a multicarriertransmitting apparatus 400 according to Embodiment 2 of the presentinvention, and FIG. 5 and FIG. 6 are drawings showing data allocationfor each subcarrier. This embodiment uses a communication methodcombining CDMA and multicarrier communication.

A communication method effective for the fourth generation is theOFDM-CDMA communication method combining CDMA and OFDM. The OFDM-CDMAcommunication method enables interference from other cells to be reducedby means of despreading processing, making it possible for communicationto be carried out even when interference from another cell is present,and in this respect differs greatly from OFDM, with which communicationbecomes totally impossible in the presence of interference waves. Inthis embodiment, the configuration in FIG. 4 differs from that in FIG. 1in the provision of a spreading section 401 and despreading section 402.Other component parts in FIG. 4 are identical to those in FIG. 1 and areassigned the same codes as in FIG. 1, and descriptions thereof areomitted.

In the OFDM-CDMA communication method, there is a method wherebysubcarriers are divided into a plurality of groups, and users areassigned to respective subcarrier groups.

Spreading section 401 performs spreading processing of transmit datainput from subcarrier allocation section 103 so that the spreading ratiois ⅕ the number of carriers, and outputs the resulting transmit data toOFDM section 104.

OFDM section 104 performs orthogonal frequency division multiplexing andgenerates an OFDM signal by executing serial-parallel conversionprocessing, followed by inverse fast Fourier transform processing andparallel-serial conversion processing, on the spread transmit data inputfrom spreading section 401, and then distributing spread chips to aplurality of subcarriers that are in a mutually orthogonal relationship,and transmits the generated OFDM signal from antenna 106 via amplifier105.

Despreading section 402 obtains receive data by executing despreadingprocessing on receive data input from demodulation section 108, andoutputs the receive data that has undergone despreading processing totransmission power control section 109.

Transmission power control section 109 determines transmission powerfrom the receive data input from despreading section 402, and performstransmission power control for amplifier 105 so that transmit data istransmitted at the determined transmission power. Transmission powercontrol section 109 performs transmission power control so that thetransmission power of systematic bit data allocated to subcarriers inthe vicinity of the center frequency is greater than the transmissionpower of parity bit data allocated to subcarriers of the frequencies atboth ends.

When spreading processing and multiplexing are performed, the spreadingratio, code multiplexing number, and number of spreading codes are madethe same for all subcarriers or all users. Here, the number of spreadingcodes is the number of spreading codes assigned to one user. The codemultiplexing number is the multiplexing number per carrier, and isdetermined by the number of users (number of codes) multiplexed.

FIG. 5 is a drawing showing the situation when code division multiplexsignals divided into five groups are allocated to subcarriers, and FIG.6 is a drawing showing grouped subcarrier allocation as in FIG. 5, bymeans of the same kind of method as in FIG. 3. Group 1 (G1) is composedof subcarriers #1 through #m, group 2 (G2) is composed of subcarriers#m+1 through #2 m, group 3 (G3) is composed of subcarriers #2 m+1through #3 m, group 4 (G4) is composed of subcarriers #3 m+1 through #4m, and group 5 (G5) is composed of subcarriers #4 m+1 through #5 m.Frequency range W10 includes group 1 subcarriers, frequency range W11includes group 2, 3, and 4 subcarriers, and frequency range W12 includesgroup 5 subcarriers.

In general, the effect of adjacent channel interference waves isgreatest for group 1 and 5 subcarriers, next greatest for group 2 and 4subcarriers, and least for group 3 subcarriers. Therefore, parity bitdata for which normal quality is sufficient is allocated to group 1 and5 subcarriers, and systematic bit data for which good quality isrequired is allocated to group 2, 3, and 4 subcarriers.

Next, examples will be described other than the case where the spreadingratio, code multiplexing number, and number of spreading codes are madethe same for all subcarriers or all users when performing spreadingprocessing and multiplexing, as described above. The following methodscan be applied as examples other than the case where the spreadingratio, code multiplexing number, and number of spreading codes are madethe same for all subcarriers or all users.

First, a case will be described in which the spreading ratio is variedaccording to the transmit data. It is possible for spreading section 401to select any spreading ratio. It is also possible for spreading section401 to select the spreading ratios for systematic bit data and paritybit data independently, and perform spreading processing of systematicbit data and parity bit data independently using the selected spreadingratios. When the spreading ratio is made larger, the spread chip taplength for one symbol is increased, enabling despreading precision to beimproved, and transmit data to be restored with a high degree ofprecision on the receiving side.

Therefore, based on FIG. 5 and FIG. 6, the spreading ratio of systematicbit data allocated to groups 2, 3, and 4 comprising subcarriers in thevicinity of the center frequency is made greater than the spreadingratio of parity bit data allocated to groups 1 and 5 comprisingsubcarriers of the frequencies at both ends. This embodiment is notlimited to the case where the spreading ratio of systematic bit data ismade greater than the spreading ratio of parity bit data, and thespreading ratio of parity bit data may be made greater than thespreading ratio of systematic bit data.

Next, a case will be described in which the code multiplexing number isvaried according to the transmit data. It is possible for OFDM section104 to select any code multiplexing number. It is also possible for OFDMsection 104 to select the code multiplexing numbers for systematic bitdata and parity bit data independently, and perform code multiplexing ofsystematic bit data and parity bit data independently using the selectedcode multiplexing numbers. A subcarrier for which the code multiplexingnumber is made small has lower transmission power than othersubcarriers. It is therefore possible to further increase thetransmission power, and to further improve error rate characteristicswhen there are adjacent channel interference waves or there is analogfilter degradation.

Therefore, based on FIG. 5 and FIG. 6, the code multiplexing number ofsystematic bit data allocated to groups 2, 3, and 4 comprisingsubcarriers in the vicinity of the center frequency is made smaller thanthe code multiplexing number of parity bit data allocated to groups 1and 5 comprising subcarriers of the frequencies at both ends. Thisembodiment is not limited to the case where the code multiplexing numberof systematic bit data is made smaller than the code multiplexing numberof parity bit data, and the code multiplexing number of parity bit datamay be made smaller than the code multiplexing number of systematic bitdata.

Next, a case will be described in which the assigned number of spreadingcodes is varied according to the transmit data. It is possible forspreading section 401 to select any number of spreading codes. It isalso possible for spreading section 401 to select the assigned number ofspreading codes for systematic bit data and parity bit dataindependently, and perform spreading processing of systematic bit dataand parity bit data independently using the selected number of spreadingcodes. In a multipath environment, orthogonality between spreading codesis lost due to delayed waves, but the loss of orthogonality may be greator small depending on the spreading codes. Consequently, multicodetransmission enables a diversity effect to be obtained and makes itpossible to further improve error rate characteristics.

Therefore, based on FIG. 5 and FIG. 6, the code multiplexing number ofsystematic bit data allocated to groups 2, 3, and 4 comprisingsubcarriers in the vicinity of the center frequency is made greater thanthe code multiplexing number of parity bit data allocated to groups 1and 5 comprising subcarriers of the frequencies at both ends. Thisembodiment is not limited to the case where the number of spreadingcodes assigned to systematic bit data is made greater than the number ofspreading codes assigned to parity bit data, and the number of spreadingcodes assigned to parity bit data may be made greater than the number ofspreading codes assigned to systematic bit data.

Here, subcarrier frequency range W11 to which systematic bit data isallocated is changed according to the adjacent channel interference wavereception level That is to say, when the adjacent channel interferencewave reception level is high, frequency range W11 to which systematicbit data is allocated is made narrower, and when the adjacent channelinterference wave reception level is low, frequency range W11 to whichsystematic bit data is allocated is made wider. The subcarriersdistributed among groups 1 through 5 are also changed in accordance withchanges of frequency range W11.

Thus, according to a multicarrier transmitting apparatus andmulticarrier transmitting method of this embodiment, in addition to theprovision of the effects of above-described Embodiment 1, transmissionis performed by means of an OFDM-CDMA communication method wherebytransmit data undergoes spreading processing and orthogonal frequencydivision multiplexing, enabling error rate characteristics to beimproved even when interference from another cell is present withoutlowering spectral efficiency. Also, when the spreading ratio ofsystematic bit data is made greater than the spreading ratio of paritybit data, systematic bit data can be restored with a high degree ofprecision on the receiving side, making it possible to improve the errorrate characteristics of systematic bit data for which good quality isrequired. When the code multiplexing number of systematic bit data ismade smaller than the code multiplexing number of parity bit data, it ispossible to increase the transmission power of systematic bit data,making it possible to improve the error rate characteristics ofsystematic bit data for which good quality is required. Furthermore,when the code multiplexing number of systematic bit data is made greaterthan the code multiplexing number of parity bit data, it is possible toimprove the error rate characteristics of systematic bit data for whichgood quality is required through a diversity effect in the systematicbit data.

In this embodiment, subcarriers are divided into five groups, butsubcarriers need not necessarily be divided into five groups, and thenumber of groups may be other than five. Also, transmit data is notlimited to systematic bit data and parity bit data, and may be dataother than systematic bit data and parity bit data for which therequired quality differs. In this case, a coder other than a turbo codercan be used for coding section 101.

Embodiment 3

FIG. 7 is a drawing showing the configuration of a multicarriertransmitting apparatus 700 according to Embodiment 3 of the presentinvention, and FIG. 8 is a drawing showing the configuration of acontrol section 702. A feature of this embodiment is that turbo code isused as an error correction code, and systematic bit data and parity bitdata are adaptively modulated independently.

In this embodiment, the configuration in FIG. 7 differs from that inFIG. 1 in that a modulation section 701 is composed of a modulationsection 701 a and modulation section 701 b, and control section 702 isprovided. Other component parts in FIG. 4 are identical to those in FIG.1 and are assigned the same codes as in FIG. 1, and descriptions thereofare omitted.

Control section 702 outputs to modulation section 701 a and modulationsection 701 b control signals specifying modulation methods set based onan RSSI (Received Signal Strength Indicator) signal level. When settingmodulation methods, control section 702 uses two threshold values: athreshold value α for setting the modulation method when modulatingsystematic bit data, and a threshold value β for setting the modulationmethod when modulating parity bit data. If the RSSI signal level isgreater than or equal to threshold value α, channel quality is estimatedto be good, and a control signal setting the 16QAM modulation method asthe systematic bit data modulation method is output to modulationsection 701 a. If the RSSI signal level is greater than or equal tothreshold value β, channel quality is estimated to be good, and acontrol signal setting the 16QAM modulation method as the parity bitdata modulation method is output to modulation section 701 b.

On the other hand, if the RSSI signal level is less than threshold valueα, control section 702 estimates that channel quality has fallen, andoutputs a control signal setting the QPSK modulation method as thesystematic bit data modulation method to modulation section 701 a.Similarly, if the RSSI signal level is less than threshold value β,control section 702 estimates that channel quality has fallen, andoutputs a control signal setting the QPSK modulation method as theparity bit data modulation method to modulation section 701 b. Ifcommunication is currently in progress and the modulation methodcurrently being used continues to be used as a result of thedetermination by control section 702, control section 702 does notoutput control signals to modulation section 701 a and modulationsection 701 b. The configuration of control section 702 will bedescribed in detail later herein.

Based on a control signal input from control section 702, modulationsection 701 a performs QPSK modulation or 16QAM modulation on systematicbit data input from coding section 101, and outputs the resulting datato subcarrier allocation section 103.

Based on a control signal input from control section 702, modulationsection 701 b performs QPSK modulation or 16QAM modulation on parity bitdata input from coding section 101, and outputs the resulting data tosubcarrier allocation section 103.

The configuration of control section 702 will now be described in detailusing FIG. 8. Control section 702 is mainly composed of a firstdetermination control section 801 and a second determination controlsection 802.

If the RSSI signal level is greater than or equal to previously setthreshold value α, first determination control section 801 outputs acontrol signal setting 16QAM as the modulation method to modulationsection 701 a. If, on the other hand, the RSSI signal level is less thanthreshold value α (not shown), first determination control section 801outputs a control signal setting QPSK as the modulation method tomodulation section 701 a.

If the RSSI signal level is greater than or equal to previously setthreshold value β, second determination control section 802 outputs acontrol signal setting 16QAM as the modulation method to modulationsection 701 b. If, on the other hand, the RSSI signal level is less thanthreshold value β (not shown), second determination control section 802outputs a control signal setting QPSK as the modulation method tomodulation section 701 b.

As systematic bit data requires better communication quality than paritybit data, threshold value α is set to a higher RSSI signal level thanthreshold value β.

In modulation sections 701 a and 701 b, systematic bit data and paritybit data that have been adaptively modulated independently undergoorthogonal frequency division multiplexing in OFDM section 104, afterwhich parity bit data is allocated to subcarriers in the vicinity ofboth ends, and systematic bit data is allocated to subcarriers in thevicinity of center frequency F1.

Thus, according to a multicarrier transmitting apparatus andmulticarrier transmitting method of this embodiment, in addition to theprovision of the effects of above-described Embodiment 1, systematic bitdata and parity bit data are adaptively modulated according to channelquality, so that by modulating systematic bit data for which goodquality is required by means of a modulation method with a small M-arymodulation number, and modulating parity bit data by means of amodulation method with a large M-ary modulation number, it is possibleto reduce degradation of parity bit data error rate characteristics eventhough parity bit data is allocated to subcarriers in the vicinity ofboth ends. Also, as systematic bit data and parity bit data areadaptively modulated according to channel quality, it is possible toachieve both an improvement in error rate characteristics and animprovement in transmission efficiency. Furthermore, in control section702, systematic bit data and parity bit data are compared with differentthreshold values a and I, providing a flexible response to variations inchannel quality, and enabling both an improvement in error ratecharacteristics and an improvement in transmission efficiency to beachieved.

In this embodiment, both systematic bit data and parity bit data areadaptively modulated, but this is not a limitation, and it is alsopossible to use a fixed modulation method for either systematic bit dataor parity bit data, and perform adaptive modulation only for the other.In this embodiment, also, control section 702 compares an RSSI signallevel with threshold value α and threshold value β, but this is not alimitation, and it is also possible for a signal, etc., indicatingchannel quality other than an RSSI signal to be compared with thresholdvalue α and threshold value β. Furthermore, in this embodiment,threshold value α and threshold value β are different values, but thisis not a limitation, and threshold value α and threshold value β may beset to the same value, or the value of threshold value α may be madesmaller than the value of threshold value β. Moreover, adaptivemodulation may be performed by means of a modulation method other than16QAM or QPSK, such as BPSK. Also, systematic bit data is modulated bymodulation section 701 a and parity bit data is modulated by modulationsection 701 b, but this is not a limitation, and systematic bit data andparity bit data may be adaptively modulated independently by a singlemodulation section. Furthermore, transmit data is not limited tosystematic bit data and parity bit data, and may be data other thansystematic bit data and parity bit data for which the required qualitydiffers. In this case, a coder other than a turbo coder can be used forcoding section 101.

Embodiment 4

FIG. 9 is a drawing showing the configuration of a multicarriertransmitting apparatus 900 according to Embodiment 4 of the presentinvention. A feature of this embodiment is that, in addition to turbocode being used as an error correction code, and systematic bit data andparity bit data being adaptively modulated independently, the modulationmethod is set for parity bit data based on a comparison of the adjacentchannel interference wave reception level with a threshold value β.

In this embodiment, the configuration in FIG. 9 differs from that inFIG. 1 in that a modulation section 701 is composed of a modulationsection 701 a and modulation section 701 b, and control sections 901 and902 are provided. Other component parts in FIG. 9 are identical to thosein FIG. 1 and are assigned the same codes as in FIG. 1, and descriptionsthereof are omitted. The configurations and operation of modulationsection 701 a and 701 b are the same as in Embodiment 3 above, andtherefore descriptions thereof are omitted.

Control section 901 outputs to modulation section 701 a a control signalspecifying a modulation method set based on an RSSI signal level. Thatis to say, if the RSSI signal level is greater than or equal to athreshold value α, control section 901 outputs to modulation section 701a a control signal setting the 16QAM modulation method as the systematicbit data modulation method.

If, on the other hand, the RSSI signal level is less than thresholdvalue α, control section 901 outputs to modulation section 701 a acontrol signal setting the QPSK modulation method as the systematic bitdata modulation method.

Control section 902 outputs to modulation section 701 b a control signalspecifying a modulation method set based on the adjacent channelinterference wave reception level. That is to say, if the adjacentchannel interference wave reception level is greater than or equal to athreshold value β, control section 902 outputs to modulation section 701b a control signal setting the QPSK modulation method as the parity bitdata modulation method. Methods for measuring the adjacent channelinterference wave reception level include, for example, detecting thelevel difference before and after an adjacent channel elimination filterof a radio section (not shown) is detected, or switching the frequencyto an adjacent channel frequency in a time period in which neithertransmission not reception is being performed and measuring the level.

If, on the other hand, the adjacent channel interference wave receptionlevel is less than threshold value β, control section 902 outputs tomodulation section 701 b a control signal setting the 16 QAM modulationmethod as the parity bit data modulation method.

Thus, according to a multicarrier transmitting apparatus andmulticarrier transmitting method of this embodiment, in addition to theprovision of the effects of above-described Embodiment 1 and Embodiment3, parity bit data is adaptively modulated according to the adjacentchannel interference wave reception level, so that when the adjacentchannel interference wave reception level is high, parity bit data canbe modulated by means of a modulation method with a small M-arymodulation number, making it possible to reduce degradation of paritybit data error rate characteristics even though parity bit data isallocated to subcarriers in the vicinity of both ends.

In this embodiment, both systematic bit data and parity bit data areadaptively modulated, but this is not a limitation, and it is alsopossible to use a fixed modulation method for either systematic bit dataor parity bit data, and perform adaptive modulation only for the other.In this embodiment, also, control section 901 compares an RSSI signallevel with threshold value α, but this is not a limitation, and it isalso possible for a signal, etc., indicating channel quality other thanan RSSI signal to be compared with threshold value α, and, for example,for the adjacent channel interference wave reception level to becompared with threshold value a. Moreover, adaptive modulation may beperformed by means of a modulation method other than 16QAM or QPSK.Also, systematic bit data is modulated by modulation section 701 a andparity bit data is modulated by modulation section 701 b, but this isnot a limitation, and systematic bit data and parity bit data may beadaptively modulated independently by a single modulation section.Furthermore, transmit data is not limited to systematic bit data andparity bit data, and may be data other than systematic bit data andparity bit data for which the required quality differs. In this case, acoder other than a turbo coder can be used for coding section 101.

Embodiment 5

FIG. 10 is a drawing showing the configuration of a multicarriertransmitting apparatus 1000 according to Embodiment 5 of the presentinvention. The further a user is, comparatively, from a base station,the stronger is the effect of adjacent channel interference waves frommany cells, and therefore the greater is the degradation of channelquality. A feature of this embodiment is that data of a usercomparatively far from a base station is allocated to subcarriers in thevicinity of the center frequency.

In this embodiment, the configuration in FIG. 10 differs from that inFIG. 1 in the provision of a serial-parallel (hereinafter referred to as“S/P”) conversion section 1001. Other component parts in FIG. 10 areidentical to those in FIG. 1, and therefore descriptions thereof areomitted.

Based on user information input from a user information storage section(not shown), S/P conversion section 1001 divides transmit data intotransmit data to be transmitted to nearby users and transmit data to betransmitted to distant users, and outputs the respective transmit datato subcarrier allocation section 103.

Subcarrier allocation section 103 performs rearrangement of the transmitdata so that transmit-data to be transmitted to nearby users isallocated to subcarriers in frequency range W1 in FIG. 3, and transmitdata to be transmitted to distant users is allocated to subcarriers infrequency range W2, and outputs the rearranged transmit data to OFDMsection 104.

Thus, according to a multicarrier transmitting apparatus andmulticarrier transmitting method of this embodiment, transmit data to betransmitted to distant users is allocated to subcarriers in the vicinityof the center frequency, and transmit data to be transmitted to nearbyusers is allocated to subcarriers in the vicinity of both ends, enablingthe channel quality of transmit data of a user comparatively far from abase station to be improved without lowering transmission efficiency.Also, transmission power control is performed so that the transmissionpower of transmit data to be transmitted to distant users allocated tosubcarriers in the vicinity of the center frequency is greater than thetransmission power of transmit data to be transmitted to nearby usersallocated to subcarriers of the frequencies at both ends, enabling theerror rate characteristics of transmit data to be transmitted to distantusers to be improved.

According to this embodiment, adaptation is possible to both the casewhere error correction is performed using a turbo coder and the casewhere error correction is performed using a coder other than a turbocoder. When error correction is performed using a turbo coder,systematic bit data may be further allocated to subcarriers in thevicinity of the center frequency among subcarriers to which transmitdata of users comparatively far from a base station is allocated. Also,in this embodiment, transmit data output from S/P conversion section1001 is divided into two—transmit data of users near a base station, andtransmit data of users comparatively far from a base station—but this isnot a limitation, and transmit data may be output divided into three ormore kinds of transmit data according to the distance of a user, etc.

Embodiment 6

FIG. 11 is a drawing showing the configuration of a multicarriertransmitting apparatus 1100 according to Embodiment 6 of the presentinvention. A feature of this embodiment is that, after systematic bitdata and parity bit data are independently interleaved, rearrangement isperformed in order to allocate systematic bit data and parity bit datato respective subcarriers.

With a communication method using conventional multicarriertransmission, interleaving can be performed in the frequency axisdirection, and therefore interleaving is performed en bloc for allsubcarriers. However, with this kind of conventional method, some datafor which better quality is required than for ordinary data is allocatedto subcarriers in the vicinity of both ends, and therefore the errorrate improvement effect for data for which better quality is requiredthan for ordinary data decreases.

In this embodiment, the configuration in FIG. 11 differs from that inFIG. 1 in the provision of interleaving sections 1101 and 1102. Othercomponent parts in FIG. 11 are identical to those in FIG. 1, andtherefore descriptions thereof are omitted.

Interleaving section 1101 interleaves systematic bit data turbo coded bycoding section 101, and outputs the resulting data to modulation section102.

Interleaving section 1102 interleaves parity bit data turbo coded bycoding section 101, and outputs the resulting data to modulation section102.

Thus, according to a multicarrier transmitting apparatus andmulticarrier transmitting method of this embodiment, in addition to theprovision of the effects of above-described Embodiment 1, rearrangementof transmit data is performed by subcarrier allocation section 103 aftersystematic bit data and parity bit data have been independentlyinterleaved, making it possible to prevent systematic bit data frombeing allocated to subcarriers of the frequencies at both ends by meansof interleaving, and so enabling the error rate characteristics ofsystematic bit data to be improved. Also, as a result of performinginterleaving, it is possible for parity bit data to be demodulatedcorrectly even if errors occur successively in parity bit data allocatedto subcarriers of the frequencies at both ends, which are susceptible tothe effects of adjacent channel interference waves. Furthermore, it ispossible for systematic bit data to be demodulated correctly even iferrors occur successively in systematic bit data allocated tosubcarriers in the vicinity of center frequency F1.

In this embodiment, error correction is performed using a turbo coder,but this is not a limitation, and it is also possible to perform errorcorrection using a coder other than a turbo coder, then divide transmitdata into transmit data for which good quality is required and transmitdata for which normal quality is sufficient, and independentlyinterleave the transmit data for which good quality is required and thetransmit data for which normal quality is sufficient.

Embodiment 7

FIG. 12 is a drawing showing transmit data allocation for eachsubcarrier according to Embodiment 7 of the present invention.Generally, with a radio apparatus using the OFDM-CDMA communicationmethod, DC offset is generated by analog circuitry provided in anamplifier of the radio transmitting section (not shown), and thereforethe error rate of a signal transmitted by a subcarrier in the vicinityof the DC point degrades more than the error rate of a signaltransmitted by other subcarriers.

Focusing on this point, this embodiment makes provisions so thattransmit data for which good quality is required is not allocated to thesubcarrier that contains the DC point. The configuration of themulticarrier transmitting apparatus is identical to the configuration inFIG. 1, and therefore a description thereof is omitted.

Subcarrier allocation section 103 performs rearrangement of transmitdata so that systematic bit data for which good quality is required isallocated to ranges W21 and W22 in the vicinity of center frequency F1,excluding subcarrier 1201 containing the DC point P1, and parity bitdata is allocated to ranges W20 and W23 in the vicinity of both ends andsubcarrier 1201 containing DC point P1. Transmit data that has undergoneorthogonal frequency division multiplexing by OFDM section 104 is thenallocated to subcarriers as shown in FIG. 12.

Subcarrier frequency ranges W21 and W22 to which systematic bit data isallocated are changed according to the adjacent channel interferencewave reception level. That is to say, when the adjacent channelinterference wave reception level is high, frequency ranges W21 and W22to which systematic bit data is allocated are made narrower, and whenthe adjacent channel interference wave reception level is low, frequencyranges W21 and W22 to which systematic bit data is allocated are madewider.

Thus, according to a multicarrier transmitting apparatus andmulticarrier transmitting method of this embodiment, in addition to theprovision of the effects of above-described Embodiment 1, systematic bitdata is not allocated to the center frequency F1 subcarrier, making itpossible to prevent degradation of error rate characteristics due to theeffects of DC offset.

In this embodiment, it has been assumed that DC point P1 is at the samefrequency as center frequency F1, but this embodiment is not limited tothe case where DC point P1 is at the same frequency as center frequencyF1, and is also applicable to a case where the DC point and centerfrequency are at different frequencies. Also, in this embodiment,transmit data is not limited to systematic bit data and parity bit data,and may be data other than systematic bit data and parity bit data forwhich the required quality differs. In this case, a coder other than aturbo coder can be used for coding section 101.

Embodiment 8

FIG. 13 is a drawing showing the configuration of a multicarriertransmitting apparatus 1300 according to Embodiment 8 of the presentinvention. A feature of this embodiment is that, in a transmittingapparatus that uses turbo code as an error correction code, adaptivelymodulates systematic bit data and parity bit data independently, andallocates parity bit data to subcarriers in the vicinity of both ends,provision is made for some of the subcarriers to which parity bit datais allocated not to be transmitted based on an RSSI signal.

In this embodiment, the configuration in FIG. 13 differs from that inFIG. 1 in the provision of a selection section 1301. Component parts inFIG. 13 identical to those in FIG. 1 are assigned the same codes as inFIG. 1, and descriptions thereof are omitted.

From the parity bit data allocated to subcarriers in the vicinity ofboth ends in the rearranged transmit data input from subcarrierallocation section 103, selection section 1301 selects null signals inplace of parity bit data when the timing arrives for input of parity bitdata allocated to subcarriers not to be transmitted, and outputs paritybit data including the selected null signals, and systematic bit data,to OFDM section 104.

When selecting parity bit data, based on an input RSSI signal, selectionsection 1301 makes the number of selected null signals small whenchannel quality is poor since the number of subcarriers not to betransmitted is made small, and makes the number of selected null signalslarge when channel quality is good since the number of subcarriers notto be transmitted is made large.

With regard to OFDM or MC-CDMA unwanted frequency components, side lobesat both ends are predominant. FIG. 14 shows the signal spectrum for onesubcarrier. As shown in FIG. 14, side lobe components are larger thenearer they are to the main lobe. In actuality, there is a sequence ofspectra as shown in FIG. 14 corresponding to the number of subcarriersas shown in FIG. 15, and therefore unwanted frequency components—thatis, side lobe components—of subcarriers at both ends are predominant.Thus, by allocating parity bit data to subcarriers in the vicinity ofboth ends and not transmitting a number of subcarriers to which paritybit data has been allocated, it is also possible to further reduce sidelobe components. It is therefore also possible to further reduceunwanted frequency components.

After transmit data has undergone orthogonal frequency divisionmultiplexing processing by OFDM section 104, parity bit data isallocated to frequency ranges W30 and W32, and systematic bit data isallocated to frequency range W31, as shown in FIG. 16. Here, subcarriers1401, 1402, 1403, and 1404 are subcarriers that are not transmitted, andnull signals are transmitted instead of subcarriers 1401, 1402, 1403,and 1404.

With a multicarrier communication method such as OFDM or MC-CDMA, thereis a problem of degradation of error rate characteristics when a numberof subcarriers are not transmitted as a way of reducing peak power. Whenturbo code is used as an error correction code, better quality isrequired for systematic bit data than for parity bit data. Therefore, bynot transmitting subcarriers to which parity bit data is allocated, itis possible to achieve compatibility between error rate characteristicsand a decrease in peak power.

Thus, according to a multicarrier transmitting apparatus andmulticarrier transmitting method of this embodiment, in addition to theprovision of the effects of above-described Embodiment 1, a certainamount of parity bit data allocated to subcarriers in the vicinity ofboth ends is not transmitted, and the data not transmitted is parity bitdata that does not require such high quality as systematic bit data, sothat it is possible to decrease peak power and reduce out-of-bandleakage with almost no degradation of the error rate.

In this embodiment, null signal selection is based on an RSSI signal,but this is not a limitation, and null signal selection can be performedusing any channel quality information. Also, in this embodiment, thenumber of subcarriers not transmitted is four, but this is not alimitation, and it is possible for any number of subcarriers not to betransmitted, and also for the subcarriers that are not to be transmittedto be selected arbitrarily.

Embodiment 9

FIG. 17 is a drawing showing the configuration of a multicarriertransmitting apparatus 1700 according to Embodiment 9 of the presentinvention. A feature of this embodiment is that, in a selection section,provision is made for some of the subcarriers to which parity bit datais allocated not to be transmitted based on delay distributioninformation.

In this embodiment, the configuration in FIG. 17 differs from that inFIG. 1 in the provision of a selection section 1701. Component parts inFIG. 17 identical to those in FIG. 1 are assigned the same codes as inFIG. 1, and descriptions thereof are omitted.

From the parity bit data allocated to subcarriers in the vicinity ofboth ends in the rearranged transmit data input from subcarrierallocation section 103, selection section 1701 selects, based on delaydistribution information, null signals in place of parity bit data whenthe timing arrives for input of parity bit data allocated to subcarriersnot to be transmitted, and outputs parity bit data including theselected null signals, and systematic bit data, to OFDM section 104.

When selecting parity bit data, based on input delay distributioninformation, selection section 1701 makes the number of selected nullsignals small when delay distribution is large since the number ofsubcarriers not to be transmitted is made small, and makes the number ofselected null signals large when delay distribution is small since thenumber of subcarriers not to be transmitted is made large. Delaydistribution information is reported by being included in a transmitsignal from a communicating party, and is therefore extracted from areceived signal.

Delay distribution information generation section 1800 will now bedescribed using FIG. 18. Delay distribution information generationsection 1800 is mainly composed of a delay circuit 1801, subtractioncircuit 1802, absolute value generation circuit 1803, and averagingcircuit 1804.

Delay circuit 1801 has as input a signal in which the preamble of areceived signal has undergone FFT processing, applies delay to the inputsignal, and outputs the signal to subtraction circuit 1802.

Subtraction circuit 1802 calculates the difference in signal levels ofadjacent subcarriers, and outputs the result to absolute valuegeneration circuit 1803.

Absolute value generation circuit 1803 converts the subtraction resultinput from subtraction circuit 1802 to an absolute value, and outputsthis absolute value to averaging circuit 1804.

Averaging circuit 1804 averages absolute values of reception leveldifferences input from absolute value generation circuit 1803 for thenumber of subcarriers, and delay distribution information is obtained.The delay distribution information obtained in this way is transmittedincluded in a transmit signal by the communicating party.

Delay distribution information is not limited to the case where it isfound by a communicating party and reported by the communicating party,and delay distribution may be detected from a received signal using thecircuit in FIG. 18. The case where delay distribution is detected from areceived signal is possible with the TDD communication method or thelike. Transmit data allocated to subcarriers after orthogonal frequencydivision multiplexing processing by OFDM section 104 is identical tothat in FIG. 16, and therefore a description thereof is omitted.

Thus, according to a multicarrier transmitting apparatus andmulticarrier transmitting method of this embodiment, in addition to theprovision of the effects of above-described Embodiment 1, a certainamount of parity bit data allocated to subcarriers in the vicinity ofboth ends is not transmitted, and the data not transmitted is parity bitdata that does not require such high quality as systematic bit data, sothat it is possible to decrease peak power and reduce out-of-bandleakage with almost no degradation of the error rate. Also, since paritybit data allocated to subcarriers that are transmitted is selected basedon delay distribution information, it is possible to prevent anexcessive increase in peak power and increased out-of-band leakage ordegradation of error rate characteristics due to an inadvertent changeof the number of subcarriers not transmitted when it is not necessary tochange the number of subcarriers not transmitted as transmit data delayis temporary.

Embodiment 10

FIG. 19 is a drawing showing the configuration of a multicarriertransmitting apparatus 1900 according to Embodiment 10 of the presentinvention. A feature of this embodiment is that, in a selection section,provision is made for some of the subcarriers to which parity bit datais allocated not to be transmitted based on reception level information.

In this embodiment, the configuration in FIG. 19 differs from that inFIG. 1 in the provision of a selection section 1901. Component parts inFIG. 19 identical to those in FIG. 1 are assigned the same codes as inFIG. 1, and descriptions thereof are omitted.

When TDD is used as the access method, the propagation path is the samefor the uplink and downlink, and therefore there is also a methodwhereby subcarriers whose reception level has fallen are given priorityfor non-transmission. By giving priority for non-transmission tosubcarriers whose reception level has fallen, it is possible to furtherachieve both a reduction of error rate characteristic degradation andpeak power, and a reduction of unwanted frequency components.

From the parity bit data allocated to subcarriers in the vicinity ofboth ends in the rearranged transmit data input from subcarrierallocation section 103, selection section 1901 selects, based onreception level information, null signals in place of parity bit datawhen the timing arrives for input of parity bit data allocated tosubcarriers not to be transmitted, and outputs parity bit data includingthe selected null signals, and systematic bit data, to OFDM section 104.

When selecting parity bit data, based on input reception levelinformation for each subcarrier, selection section 1901 selects nullsignals in place of parity bit data allocated to subcarriers whosereception level has fallen, and selects systematic bit data and paritybit data including null signals. Any method can be used to determinewhether or not the reception level has fallen, such as determination bymeans of a predetermined threshold value, or relative determination bycomparison with the reception levels of other subcarriers. Transmit dataallocated to subcarriers after orthogonal frequency divisionmultiplexing processing by OFDM section 104 is identical to that in FIG.16, and therefore a description thereof is omitted.

Thus, according to a multicarrier transmitting apparatus andmulticarrier transmitting method of this embodiment, in addition to theprovision of the effects of above-described Embodiment 1, a certainamount of parity bit data allocated to subcarriers in the vicinity ofboth ends is not transmitted, and the data not transmitted is parity bitdata that does not require such high quality as systematic bit data, sothat it is possible to decrease peak power and reduce out-of-bandleakage with almost no degradation of the error rate. Also, since nullsignals are selected based on reception level information, parity bitdata allocated to subcarriers whose reception level has fallen is nottransmitted when transmission is next performed, it is possible tofurther achieve compatibility between error rate characteristics and adecrease in peak power and reduction of unwanted frequency components.

Embodiment 11

FIG. 20 is a drawing showing the configuration of a multicarriertransmitting apparatus 2000 according to Embodiment 11 of the presentinvention. A feature of this embodiment is that, in a selection section,provision is made for some of the subcarriers to which parity bit datais allocated not to be transmitted based on adjacent channelinterference wave reception level information.

In this embodiment, the configuration in FIG. 20 differs from that inFIG. 1 in the provision of a selection section 2001. Component parts inFIG. 20 identical to those in FIG. 1 are assigned the same codes as inFIG. 1, and descriptions thereof are omitted.

A method whereby the adjacent channel interference wave reception levelis also taken into consideration in determining the number ofsubcarriers not to be transmitted is also effective. The higher theadjacent channel interference wave reception level, the poorer is thequality of subcarriers at both ends. Therefore, with regard tosubcarriers at both ends, error rate characteristics may actually beimproved by increasing the number of subcarriers not transmitted.Moreover, it goes without saying that peak power and unwanted frequencycomponents are naturally also reduced.

In the rearranged transmit data input from subcarrier allocation section103, selection section 2001 selects null signals in place of parity bitdata allocated to subcarriers at both ends for which the effect ofadjacent channel interference wave reception levels is greatest, andoutputs systematic bit data, and parity bit data including the selectednull signals, to OFDM section 104.

After transmit data has undergone orthogonal frequency divisionmultiplexing processing by OFDM section 104, parity bit data isallocated to frequency ranges W40 and W42, and systematic bit data isallocated to frequency range W41, as shown in FIG. 21. Here, subcarriers2101 and 2102 at either end are subcarriers that are not transmitted,and null signals are transmitted instead of subcarriers 2101 and 2102.

Thus, according to a multicarrier transmitting apparatus andmulticarrier transmitting method of this embodiment, in addition to theprovision of the effects of above-described Embodiment 1, a certainamount of parity bit data allocated to subcarriers in the vicinity ofboth ends is not transmitted, and the data not transmitted is parity bitdata that does not require such high quality as systematic bit data, sothat it is possible to decrease peak power and reduce out-of-bandleakage with almost no degradation of the error rate. Also, sincesubcarriers at both ends for which the effect of adjacent channelinterference wave reception levels is greatest are not transmitted, itis possible to decrease peak power and reduce out-of-band leakagewithout degrading error rate characteristics.

In this embodiment, the number of subcarriers not transmitted is two,but the number of subcarriers not transmitted is not limited to two, andit is possible for any number of subcarriers toward the center frequencyfrom either end not to be transmitted.

The multicarrier transmitting apparatuses and multicarrier transmittingmethods in above-described Embodiment 1 through Embodiment 11 can beapplied to a base station apparatus and a communication terminalapparatus.

As described above, according to the present invention, it is possibleto improve significantly the error rate characteristics of transmit datafor which good quality is required, and prevent degradation of thequality of transmit data for which good quality is required.

This application is based on Japanese Patent Application No. 2002-297534filed on Oct. 10, 2002, and Japanese Patent Application No. 2003-7616filed on Jan. 15, 2003, the entire content of which is expresslyincorporated by reference herein.

INDUSTRIAL APPLICABILITY

The present invention is applicable to a multicarrier transmittingapparatus and multicarrier transmitting method.

1. A multicarrier transmitting apparatus comprising: a dividing sectionthat divides transmit data into high-quality transmit data for whichgood quality is required and ordinary transmit data other than saidhigh-quality transmit data; a rearranging section that rearranges saidtransmit data so that said high-quality transmit data is allocated to asubcarrier in the vicinity of a center frequency; and an orthogonalfrequency division multiplexing section that performs orthogonalfrequency division multiplexing of said transmit data rearranged by saidrearranging section and allocates said transmit data to subcarriers. 2.The multicarrier transmitting apparatus according to claim 1, furthercomprising a spreading section that performs spreading processing ofsaid transmit data rearranged by said rearranging section, wherein saidorthogonal frequency division multiplexing section performs orthogonalfrequency division multiplexing of said transmit data that has undergonespreading processing and allocates said transmit data to subcarriers. 3.The multicarrier transmitting apparatus according to claim 2, whereinsaid spreading section independently sets spreading ratios of saidhigh-quality transmit data and said ordinary transmit data.
 4. Themulticarrier transmitting apparatus according to claim 2, wherein saidspreading section makes a spreading ratio of said high-quality transmitdata greater than a spreading ratio of said ordinary transmit data. 5.The multicarrier transmitting apparatus according to claim 2, whereincode multiplexing numbers of said high-quality transmit data and saidordinary transmit data are set independently.
 6. The multicarriertransmitting apparatus according to claim 2, wherein a code multiplexingnumber of said high-quality transmit data is made smaller than a codemultiplexing number of said ordinary transmit data.
 7. The multicarriertransmitting apparatus according to claim 2, wherein numbers ofspreading codes assigned to said high-quality transmit data and saidordinary transmit data are set independently.
 8. The multicarriertransmitting apparatus according to claim 2, wherein a number ofspreading codes assigned to said high-quality transmit data is madegreater than a number of spreading codes assigned to said ordinarytransmit data.
 9. The multicarrier transmitting apparatus according toclaim 1, further comprising a modulation section that modulates saidhigh-quality transmit data and said ordinary transmit data usingindependently set modulation methods.
 10. The multicarrier transmittingapparatus according to claim 9, wherein said modulation section fixes amodulation method of either said high-quality transmit data or saidordinary transmit data, and adaptively changes a modulation method ofthe other of said high-quality transmit data or said ordinary transmitdata.
 11. The multicarrier transmitting apparatus according to claim 9,wherein said modulation section adaptively changes a modulation methodof both said high-quality transmit data and said ordinary transmit data.12. The multicarrier transmitting apparatus according to claim 9,wherein said modulation section selects a modulation method inaccordance with an adjacent channel interference wave reception level.13. The multicarrier transmitting apparatus according to claim 1,further comprising an interleaving section that independentlyinterleaves said high-quality transmit data and said ordinary transmitdata, wherein said rearranging section rearranges said transmit dataafter interleaving.
 14. The multicarrier transmitting apparatusaccording to claim 1, wherein said rearranging section rearranges saidtransmit data so that said ordinary transmit data is allocated to asubcarrier containing a DC point.
 15. The multicarrier transmittingapparatus according to claim 1, further comprising a transmission powersetting section that sets transmission power of said high-qualitytransmit data higher than transmission power of said ordinary transmitdata.
 16. The multicarrier transmitting apparatus according to claim 15,wherein said transmission power setting section sets transmission powerof said high-quality transmit data and said ordinary transmit datavariably.
 17. The multicarrier transmitting apparatus according to claim15, wherein said transmission power setting section sets transmissionpower of either said high-quality transmit data or said ordinarytransmit data variably.
 18. The multicarrier transmitting apparatusaccording to claim 15, wherein said transmission power setting sectionvaries transmission power in accordance with channel quality.
 19. Themulticarrier transmitting apparatus according to claim 1, wherein saidorthogonal frequency division multiplexing section narrows a range ofsubcarriers to which said high-quality transmit data is allocated whenan adjacent channel interference wave reception level increases.
 20. Themulticarrier transmitting apparatus according to claim 1, furthercomprising a coding section that turbo-codes said transmit data, whereinsaid high-quality transmit data is systematic bit data and said ordinarytransmit data is parity bit data.
 21. The multicarrier transmittingapparatus according to claim 1, wherein said high-quality transmit datais transmit data that is transmitted to a distant communicating party,and said ordinary transmit data is transmit data that is transmitted toa nearby communicating party.
 22. The multicarrier transmittingapparatus according to claim 1, wherein said high-quality transmit datais information used for communication control or retransmissioninformation.
 23. The multicarrier transmitting apparatus according toclaim 1, further comprising a selection section that selects saidordinary transmit data so that subcarriers to which part of saidordinary transmit data rearranged by said rearranging section and saidhigh-quality transmit data are allocated are transmitted.
 24. Themulticarrier transmitting apparatus according to claim 1, wherein saidselection section selects said ordinary transmit data so that a numberof subcarriers to which said ordinary transmit data is allocated thatare transmitted is variable.
 25. The multicarrier transmitting apparatusaccording to claim 1, wherein said selection section selects saidordinary transmit data so that a number of subcarriers to which saidordinary transmit data is allocated that are transmitted is variableaccording to channel quality.
 26. The multicarrier transmittingapparatus according to claim 1, wherein said selection section selectssaid ordinary transmit data so that a number of subcarriers to whichsaid ordinary transmit data is allocated that are transmitted isvariable based on delay distribution information of said transmit data.27. The multicarrier transmitting apparatus according to claim 1,wherein said selection section selects said ordinary transmit data thatis allocated to subcarriers of a predetermined reception level orhigher.
 28. The multicarrier transmitting apparatus according to claim1, wherein said selection section selects so that a number ofsubcarriers to which said ordinary transmit data is allocated that aretransmitted is variable in accordance with an adjacent channelinterference wave reception level.
 29. A base station apparatus that hasa multicarrier transmitting apparatus comprising: a dividing sectionthat divides transmit data into high-quality transmit data for whichgood quality is required and ordinary transmit data other than saidhigh-quality transmit data; a rearranging section that rearranges saidtransmit data so that said high-quality transmit data is allocated to asubcarrier in the vicinity of a center frequency; and an orthogonalfrequency division multiplexing section that performs orthogonalfrequency division multiplexing of said transmit data rearranged by saidrearranging section and allocates said transmit data to subcarriers. 30.A communication terminal apparatus that has a multicarrier transmittingapparatus comprising: a dividing section that divides transmit data intohigh-quality transmit data for which good quality is required andordinary transmit data other than said high-quality transmit data; arearranging section that rearranges said transmit data so that saidhigh-quality transmit data is allocated to a subcarrier in the vicinityof a center frequency; and an orthogonal frequency division multiplexingsection that performs orthogonal frequency division multiplexing of saidtransmit data rearranged by said rearranging section and allocates saidtransmit data to subcarriers.
 31. A multicarrier transmitting methodcomprising: a step of dividing transmit data into high-quality transmitdata for which good quality is required and ordinary transmit data otherthan said high-quality transmit data; a step of rearranging saidtransmit data so that said high-quality transmit data is allocated to asubcarrier in the vicinity of a center frequency; and a step ofperforming orthogonal frequency division multiplexing of rearranged saidtransmit data and allocating said transmit data to subcarriers.
 32. Themulticarrier transmitting method according to claim 31, furthercomprising a step of spreading said transmit data.
 33. The multicarriertransmitting method according to claim 31, further comprising a step ofmodulating said high-quality transmit data and said ordinary transmitdata using independently set modulation methods.
 34. The multicarriertransmitting method according to claim 33, further comprising a step ofselecting a modulation method in accordance with an adjacent channelinterference wave reception level.
 35. The multicarrier transmittingmethod according to claim 31, wherein said high-quality transmit data istransmit data that is transmitted to a distant communicating party, andsaid ordinary transmit data is transmit data that is transmitted to anearby communicating party.
 36. The multicarrier transmitting methodaccording to claim 31, further comprising a step of independentlyinterleaving said high-quality transmit data and said ordinary transmitdata.
 37. The multicarrier transmitting method according to claim 31,wherein said ordinary transmit data is selected so that subcarriers towhich part of said ordinary transmit data rearranged by said rearrangingsection and said high-quality transmit data are allocated aretransmitted.